Conventionally, in a manufacturing process of a semiconductor device, a LCD substrate, or the like, one of processing steps in a resist pattern forming process is a hydrophobicizing process performed on, e.g., a semiconductor wafer (hereinafter, simply referred to as a wafer). The hydrophobicizing process is conducted to change a hydrophilic surface of a wafer to a hydrophobic surface by spraying vapor of HMDS (hexamethyldisilazane) onto the surface of the wafer in order to improve adhesiveness between a base film and a resist film prior to coating the wafer with resist. The hydrophobicizing process may be usually performed on the surface of the wafer and a bevel portion (an end surface of outer periphery) of the wafer. By the benefit of the hydrophobicizing process, if there is performed a liquid immersion exposure process in which an exposure is carried out through water between the wafer and an exposure apparatus, it is advantageous that peeling of the resist film may be suppressed.
Patent Document 1 discloses an apparatus for performing such a hydrophobicizing process on a wafer. In this apparatus, HMDS used as a liquid chemical for a liquid source is stored in a tank, and a carrier gas supply source and a processing chamber configured to perform the hydrophobicizing process are connected to the tank via respective pipes. A carrier gas is supplied from the carrier gas supply source into the tank, so that the HMDS within the tank is bubbled and vaporized. The vaporized HMDS is carried into the processing chamber by the carrier gas.
In the meanwhile, in order to meet a demand for enhancement of throughput in the manufacturing process of the semiconductor device, processing time of the hydrophobicizing process needs to be shortened. Thus, it can be considered to improve throughput by supplying a HMDS gas (hydrophobicizing gas) of a relatively high concentration to the wafer.
Since a hydrophobicizing gas generation rate is proportional to a contact area between the HMDS and the carrier gas, it may be considered to improve throughput by using a large-size tank storing the HMDS and thus supplying a high-concentration HMDS gas to the wafer. Since, however, such a large-size tank may not be placed adjacent to the processing chamber, a pipe for connecting the processing chamber and the tank would be lengthened. If the length of the pipe is increased, the hydrophobicizing gas containing the HMDS of the relatively high concentration would be condensed while it flows through the pipe. Therefore, it is concerned that a hydrophobicizing gas of an expected concentration is not supplied to the wafer. Further, since the pipe needs to be filled with the hydrophobicizing gas whenever a wafer process is performed, sufficient throughput improvement may not be achieved. As a countermeasure to such a condensation problem, installation of a heating unit at the pipe may be considered. In such a case, however, the apparatus may be scaled up and a foot print of the apparatus may be increased.
Moreover, since the HMDS is always kept in contact with the supplied carrier gas within the tank, the HMDS and the carrier gas may react to each other in the tank if the generation of the hydrophobicizing gas is stopped for some time, resulting in degradation of the HMDS liquid. If the deterioration of the HMDS liquid occurs, the surface of the wafer may not be hydrophobicized sufficiently, and, thus, it becomes difficult to improve adhesiveness of the resist film.    Patent Document 1: Japanese Patent Laid-open Publication H11-214292 (paragraphs [0036], [0037], and [0048]).